RPC Efficiency with
Track
Reconstruction
Giuseppe Roselli
Giuseppe Roselli (CMS-RPC)
Università degli Studi di Bari – INFN
Muon Reconstruction
•
Four steps:
1.
2.
3.
4.
Digitization
Local Reconstruction
Stand Alone Reconstruction
Global Reconstruction
• In the Stand-Alone reconstruction the RPC can be excluded (or DT or CSC) giving the
possibility to reconstruct the track on the detector surface and calculate the efficiency.
• Z°-> µ+µ- samples have been used for this analysis.
Giuseppe Roselli (CMS-RPC)
Università degli Studi di Bari – INFN
1- Chamber selection
•
We can see how the chambers are selected in the
algorithm without bias:
1.
Read Trajectory (not persistent objects, that are deleted at the end of
the reconstruction chain and contains all the information on the track
propagation  need to run the reconstruction in the same job of
analysis)
2.
Loop over all the CMS RPC Roll (Barrel + EndCap)
3.
Extrapolation of the impact point on each encountered surface
4.
Coordinates conversion in the Local Frame
5.
Roll selection.
Giuseppe Roselli (CMS-RPC)
Università degli Studi di Bari – INFN
2- Efficiency - selection
•
Matching between the extrapolated point and the rechit point, can be
calculated residuals distribution, giving the possibility to estimate the RPC
resolution and understand which kind of cuts can be applied to decide the
efficiency of the single chamber.
Stand-Alone Muon Track
µ
RB1IN
RPC extrapolation
RB1out
On surface
RB2IN
Residuals
RB2out
RB3
z
RB4
Local coordinate
Giuseppe Roselli (CMS-RPC)
y
Efficiency
x
Università degli Studi di Bari – INFN
More rec-hits
• If there are more than one rec-hit we can
select the only one that gives the minimum
residual!
Best RecHit1
µ1
Giuseppe Roselli (CMS-RPC)
µ2
Best RecHit2
Università degli Studi di Bari – INFN
Parameters
•
We can decide:
1.
Kind of track to read:
2.
a)
StandAloneMuons
b)
StandAloneMuons + Vertex
c)
GlobalMuons
Set the cut value on the residuals:
a)
Default cut = 6 cm.
3.
Start directly from digi of DT or CSC and RPC.
4.
Create the following plots:
a)
Efficiency
b)
Residuals
c)
Real Occupancy and predicted from the track extrapolation
d)
Residuals vs reconstructed Pt
e)
Global Residuals and Efficiency
Giuseppe Roselli (CMS-RPC)
Università degli Studi di Bari – INFN
Results
• Residuals distribution for all the chambers:
Giuseppe Roselli (CMS-RPC)
Università degli Studi di Bari – INFN
Pull and error associated
to the Rec-Hit
• To find the functional form of the Resolution, can be investigated the
Pull distribution, defined as:
 ( x)
Pull  x

• If the estimation of σx on the average value is correct, the Pull
distribution must be fitted with a Gaussian curve having a standard
deviation of about “ 1 ”.
Giuseppe Roselli (CMS-RPC)
Università degli Studi di Bari – INFN
Pull Distribution
Errors on Rec-Hit
overestimated
Giuseppe Roselli (CMS-RPC)
Università degli Studi di Bari – INFN
Reconstructed Pt
•
Pt distribution calculated in correspondence of the RPC surface.
Giuseppe Roselli (CMS-RPC)
Università degli Studi di Bari – INFN
GREN Track Reconstruction
Giuseppe Roselli (CMS-RPC)
Università degli Studi di Bari – INFN
GREN Results
Local Efficiency with
an average value of
about 94%
Residuals
Giuseppe Roselli (CMS-RPC)
Università degli Studi di Bari – INFN
Inefficient cases
Inefficient case due to
the track reconstruction
Real Inefficient case
Giuseppe Roselli (CMS-RPC)
Università degli Studi di Bari – INFN
Stand Alone Reconstruction
•
The same package can be used also track reconstructed
only with the RPC and obtain the “Stand Alone Efficiency”.
•
Status:
1.
At the moment the RPC seed can be read and from it can be
activated the reconstruction chain (there are cases in which it
does not works and so the tracks are not reconstructed) (P. Noli)
Giuseppe Roselli (CMS-RPC)
Università degli Studi di Bari – INFN
Stand Alone options
Giuseppe Roselli (CMS-RPC)
Università degli Studi di Bari – INFN
RPC Stand Alone Residuals
Giuseppe Roselli (CMS-RPC)
Università degli Studi di Bari – INFN
RPC Stand Alone Pull
Errors on Rec-Hit
underestimated
Giuseppe Roselli (CMS-RPC)
Università degli Studi di Bari – INFN
Work in progress
•
At the moment this algorithm has been tested only on simulated data
and a real test can be done with the Cosmic Runs.
•
The main topic for the future is to evaluate the “intrinsic efficiency”
for each chamber using the following method:
1.
Match between simulated and reconstructed tracks;
2. Calculate the efficiency vs Pt;
3. Calculate the efficiency vs eta.
Giuseppe Roselli (CMS-RPC)
Università degli Studi di Bari – INFN